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During a trip on an expressway, Don drove a total of x [#permalink]
17 Nov 2006, 15:37

During a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5-mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60 miles per hour. His travel time for the x-mile trip was what percent greater than it would have been if he had traveled at a constant rate of 60 miles per hour for the entire trip?

During a trip on an expressway, Don drove a total of x miles. His average speed on a certain 5-mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60 miles per hour. His travel time for the x-mile trip was what percent greater than it would have been if he had traveled at a constant rate of 60 miles per hour for the entire trip?

I see that it is too late. I happen to come across only today.

SimaQ wrote:

Could someone say why picking numbers does not work?

suppose x=10 miles

Then....

30/60*t=5 1/2t=5 t=6 minutes for the first 5 miles t should be 10

and

60/60*t=5 t=5 minutes for the remaining 5 miles

Total 5+6=11 minutes Then total = 5+10=15

if he had travelled 60 per hour all the way; 1t=10 t=10 minutes......

So his travel time was 10% greater... so 50% greater which is 500/10%, so picking nos. too work here Include 10 instead of x in answer choices and look for 10% return.... what is wrong here?

Re: Problem Solving [#permalink]
30 Dec 2006, 20:05

i'm not getting what others are.
i solved this way.

it is only for the 5 mile section that speeds are different,namely 30 and 60 miles per hour.
for the remainder,the speed is same in both the cases.so the time spent will be same for remainder of the distance.

for the 5 mile section,t1 = 5/30 hrs
t2 = 5/60 hrs

Re: Problem Solving [#permalink]
30 Dec 2006, 23:45

AK47 wrote:

i'm not getting what others are. i solved this way.

it is only for the 5 mile section that speeds are different,namely 30 and 60 miles per hour. for the remainder,the speed is same in both the cases.so the time spent will be same for remainder of the distance.

for the 5 mile section,t1 = 5/30 hrs t2 = 5/60 hrs

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